old antifouling

[Clint]

I am in the process of removing the old antifouling from my little trailer sailer (she has been out of the water for at least 5 years, and is now undergoing a major refurb, and refit) it looks like the previous owners just slapped layer upon layer of AF on, l have already found 3 different shades of red. At the moment it's all coming off rather too easily, which is concerning me, because this only means that l am going to run into some really hard bits later on. I can see the original gelcoat underneath it all, now when reapplying new AF, does the gel coat need to be in pristine clean and shiny condition to accept primer and new AF? It all looks good under the hull so far, no signs of osmosis or any other major issues.

Clint

 

[VicS]

I am in the process of removing the old antifouling from my little trailer sailer (she has been out of the water for at least 5 years, and is now undergoing a major refurb, and refit) it looks like the previous owners just slapped layer upon layer of AF on, l have already found 3 different shades of red. At the moment it's all coming off rather too easily, which is concerning me, because this only means that l am going to run into some really hard bits later on. I can see the original gelcoat underneath it all, now when reapplying new AF, does the gel coat need to be in pristine clean and shiny condition to accept primer and new AF? It all looks good under the hull so far, no signs of osmosis or any other major issues.

Clint

It seems to flake off when the boat has been left out of the water for a couple of years or so. Dunno why.

As clean as possible but not pristine I'd say before priming and re antifouling. ... But for a trailer sailer why antifoul if its not going to stay afloat all season


Mine awaits AF removal but a guy in yard found an old plane iron, corners rounded off, and kept sharp a good tool for removing built up layers of old AF. A wipe over with AF thinner should get any residue off

 

[Clint]

It seems to flake off when the boat has been left out of the water for a couple of years or so. Dunno why.

As clean as possible but not pristine I'd say before priming and re antifouling. ... But for a trailer sailer why antifoul if its not going to stay afloat all season


Mine awaits AF removal but a guy in yard found an old plane iron, corners rounded off, and kept sharp a good tool for removing built up layers of old AF. A wipe over with AF thinner should get any residue off

Good point, and that would save me loads of money too.

 

[PuffTheMagicDragon]

Good point, and that would save me loads of money too.

Yes, an old plane iron or even a 'slick' (type of wood chisel) are excellent for removing old AF in large flakes. However, please, wear eye protection and a good mask. AF fragments in your eyes will really hurt and breathing in the inevitable dust and small particles will do nasty things to your lungs.

While at it, I would do the whole of the underwater part of the hull down to the gelcoat and then give a full coat of primer before applying the new antifoul. It gives a better finish and is not something that you will be doing every year, especially if the AF is self-polishing.

 

[Clint]

Yes, an old plane iron or even a 'slick' (type of wood chisel) are excellent for removing old AF in large flakes. However, please, wear eye protection and a good mask. AF fragments in your eyes will really hurt and breathing in the inevitable dust and small particles will do nasty things to your lungs.

While at it, I would do the whole of the underwater part of the hull down to the gelcoat and then give a full coat of primer before applying the new antifoul. It gives a better finish and is not something that you will be doing every year, especially if the AF is self-polishing.

I have just spent the last 4 hours stripping the SB side down to gelcoat, and even with my dust mask, with proper filters l still had AF dust in my nose, terrible stuff. I am struggling with the old boot strip though, it seems as this is the only part of the boat that has been applied properly. The old AF is so rotten that it comes off in minute little flakes, and dust, and that's with using an old thin paint scraper.
Should the residue be washed off, or sanded off? The last time l did any AF work was helping a friend on his powerboat many years ago, and l had almost forgotten how much l hate it. Next time l decide to buy and refurbish a boat, someone restrain me please.

 

[PuffTheMagicDragon]

Should the residue be washed off, or sanded off?

Wet-or-Dry abrasive, grit 320, used WET with copious amounts of water. There is no need to remove every minute trace of the old AF; just remove as much as you can of what we call 'maps', the stubborn raised areas that look like a relief map. It'll be worth the extra effort so don't give up now. You're more than half-way there!